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In this paper, we study the Dirac cohomology of minimal representations for all real reductive groups G. The Dirac indices of these representations are also studied when G is of equal rank, giving some counterexamples of a conjecture of…

Representation Theory · Mathematics 2024-04-29 Xuanchen Zhao

We survey different tools to classify representations of compact Lie groups according to their cohomogeneity and apply these methods to the case of irreducible representations of cohomogeneity 6, 7 and 8.

Representation Theory · Mathematics 2018-02-09 Francisco J. Gozzi

We study Dirac cohomology $H_D^{\mathfrak{g},\mathfrak{h}}(M)$ for modules belonging to category $\mathcal{O}$ of a finite dimensional complex semisimple Lie algebra. We prove Vogan's conjecture, a nonvanishing result for…

Representation Theory · Mathematics 2023-10-18 Spyridon Afentoulidis-Almpanis

We define uniformly the notions of Dirac operators and Dirac cohomology in the framework of the Hecke algebras introduced by Drinfeld. We generalize in this way the Dirac cohomology theory for Lusztig's graded affine Hecke algebras. We…

Representation Theory · Mathematics 2015-06-23 Dan Ciubotaru

In a joint paper P. Pand\v{z}i\'c and D. Renard proved that holomorphic and antiholomorphic discrete series representations can be constructed via algebraic Dirac induction. The group $SU(2,1)$, except for those two types, also has a third…

Representation Theory · Mathematics 2016-07-05 Ana Prlić

In this article, we introduce the first degrees of a cochain complex associated to a strict Lie 2-group whose cohomology is shown to extend the classical cohomology theory of Lie groups. In particular, we show that the second cohomology…

Category Theory · Mathematics 2021-03-10 Camilo Angulo

We define analogues of the Casimir and Dirac operators for graded affine Hecke algebras, and establish a version of Parthasarathy's Dirac operator inequality. We then prove a version of Vogan's Conjecture for Dirac cohomology. The…

Representation Theory · Mathematics 2010-06-22 Dan Barbasch , Dan Ciubotaru , Peter E. Trapa

A difference Lie group is a Lie group equipped with a difference operator, equivalently a crossed homomorphism with respect to the adjoint action. In this paper, first we introduce the notion of a representation of a difference Lie group,…

Rings and Algebras · Mathematics 2024-03-25 Jun Jiang , Yunnan Li , Yunhe Sheng

We exhibit a cocycle in the simplicial de Rham complex which represents the Euler class. As an application, we construct a Lie algebra cocycle on $L\mathfrak{so}(4)$.

Differential Geometry · Mathematics 2015-08-27 Naoya Suzuki

We give a construction that takes a simple linear algebraic group $G$ over a field and produces a commutative, unital, and simple non-associative algebra $A$ over that field. Two attractions of this construction are that (1) when $G$ has…

Rings and Algebras · Mathematics 2021-01-18 Maurice Chayet , Skip Garibaldi

We study the Dirac cohomology of supermodules over basic classical Lie superalgebras, formulated in terms of cubic Dirac operators associated with parabolic subalgebras. Specifically, we establish a super-analog of the Casselman-Osborne…

Representation Theory · Mathematics 2026-03-03 Simone Noja , Steffen Schmidt , Raphael Senghaas

We suggest a method of constructing special nonunitary representations of semisimple Lie groups using representations of Iwasawa subgroups. As a typical example, we study the group $U(2,2)$.

Representation Theory · Mathematics 2014-08-26 A. M. Vershik , M. I. Graev

In this paper, we review the construction of the Dirac operator for graded affine Hecke algebras and calculate the Dirac cohomology of irreducible unitary modules for the graded Hecke algebra of gl(n).

Representation Theory · Mathematics 2012-07-13 Dan Barbasch , Dan Ciubotaru

We investigate symplectic nilpotent Lie groups with Lagrangian normal subgroups. We show that there exists a bijection between the isomorphism classes of nilpotent Lie groups with Lagrangian normal subgroups and the isomorphism classes of…

Symplectic Geometry · Mathematics 2026-01-27 T. Aït Aissa , M. W. Mansouri

This paper classifies all the Dirac series (that is, irreducible unitary representations having non-zero Dirac cohomology) of $E_{7(7)}$. Enhancing the Helgason-Johnson bound in 1969 for the group $E_{7(7)}$ is one key ingredient. Our…

Representation Theory · Mathematics 2024-12-20 Yi-Hao Ding , Chao-Ping Dong , Lin Wei

In this paper, we define two generalisations of Dirac operators for Drinfeld's Hecke algebra. One generalisation, Parthasarathy operators inherit the notion of the Dirac inequality. The second generalisation, warped Dirac operators are such…

Representation Theory · Mathematics 2024-03-12 Kieran Calvert

I present several applications of the Dirac inequality to the determination of isolated unitary representations and associated "spectral gaps" in the case of unramified principal series. The method works particularly well in order to attach…

Representation Theory · Mathematics 2021-03-29 Dan Ciubotaru

We present the derivation of the 6-dimensional Eulerian Lie group of the form SO(3,C). We describe our derivation process, which involves the creation of a finite group by using permutation matrices, and the exponentiation of the adjoint…

General Mathematics · Mathematics 2018-03-20 Jason Glowney

In this paper we will derive an explicit description of the genuine projective representations of the symmetric group $S_n$ using Dirac cohomology and the branching graph for the irreducible genuine projective representations of $S_n$. In…

Representation Theory · Mathematics 2019-05-20 Kieran Calvert

The idea of using Dirac cohomology to study branching laws was initiated by Huang, Pandzi\'c and Zhu in 2013 [HPZ]. One of their results says that the Dirac cohomology of $\pi$ completely determines $\pi|_{K}$, where $\pi$ is any…

Representation Theory · Mathematics 2024-11-07 Chao-Ping Dong , Yongzhi Luan , Haojun Xu